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18 September 1996 Bridging the gap between electronic speckle pattern interferometry and holography
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Proceedings Volume 2782, Optical Inspection and Micromeasurements; (1996)
Event: Lasers, Optics, and Vision for Productivity in Manufacturing I, 1996, Besancon, France
Both electronic speckle pattern interferometry (ESPI) and holography are rather powerful tools for nondestructive testing of materials and products. ESPI and holographic interferometry allow to measure deformations and vibrations in the micrometer and submicrometer ranges. In spite of definite similarities they differ chiefly in the methods of acquiring and presenting optical data. Each method has its special advantages and drawbacks. The latter are severely limiting their applications especially in industry. It would be ideal to combine the advantages of ESPI and holography and to reduce influence of their drawbacks. As for ESPI, this method is very suited for large scale industrial optical inspections because the interferograms are acquired with a CCD camera and evaluated in quasi real time with a computer thus no media costs for the measurements arise. However current speckle pattern interferometers have rather complicated and expensive optical setups whose elements are aligned with difficulty. Moreover commercial ESPI devices lack flexibility in their optical setups. The negative influences of these drawbacks are drastically reduced in our method which is based on a very simple principle. We offer to use an unusual ESPI reference wave which is stored in a holographic optical element (HOE) as holographic object wave. In other words, a new method of ESPI is introduced which is a two stage process. At the first stage a HOE is recorded in a usual holographic arrangement. This HOE being illuminated later reconstructs an object wave which serves as ESPI reference wave. Well suited HOE's are produced on photothermoplastic or silver halide media. The latter are easily produced in an industrial environment. Experimental results and ready compact and inexpensive device are presented.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bernhard Lau and Valery Petrov "Bridging the gap between electronic speckle pattern interferometry and holography", Proc. SPIE 2782, Optical Inspection and Micromeasurements, (18 September 1996);

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